BMKG said about the circular clouds at the top of Mount Lawu, Merbabu and Merapi

SEMARANG, KOMPAS.com – Circular clouds can be seen atop Mount Merbabu, Mount Merapi, and Mount Lawu on Thursday (11/5/2020) morning.

The head of the Data and Information Section of the BMKG Climatology Station Semarang Iis W. Harmoko said that the clouds that appear at the top of the three mountains are lenticularis.

“In general, lenticularis clouds are plate- or lens-shaped clouds or groups of clouds trapped in the lower layer of the atmosphere. They are called trapped because lenticularis clouds generally appear to be stationary where they formed,” Harmoko explained when contacted. Thursday.

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It is explained that the appearance of lenticular clouds is a sign of the presence of mountain waves that are quite dangerous for the flight path.

“These mountain waves can cause turbulence to form, which is dangerous for aviation,” he said.

This lenticularis cloud, he continued, began to form when wind currents flowing parallel to the earth’s surface encountered obstacles from certain objects such as mountains.

“As a result of these obstacles, the air currents move vertically towards the top of the cloud,” he said.

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If the rising air contains a lot of water vapor and is stable, when it reaches the dew point temperature at the top of the mountain, the water vapor begins to condense into clouds following the contours of the top of the mountain.

He added that when the air passes over the top of the mountain and goes down, the condensation process stops.

“That is why the lenticularis cloud seems silent because the clouds start to form from the side of the wind direction (windward side) at the top of the mountain and then disappeared on the downwind side (lee side), “he said.